What was done
Carilli et al., as they describe it, "collected cores from massive Porites sp.
corals in the Gilbert Islands of Kiribati to investigate how corals
along a natural gradient in temperature variability responded to recent
heat stress events," in the course of which activity they "examined
changes in coral skeletal growth rates and partial mortality scars
(Carilli et al., 2010) to investigate the impact of the
bleaching event in 2004 (Donner, 2011) on corals from different
temperature variability regimes."

What it means
In the concluding sentence of their paper's abstract, Carilli et al.
say their study indicates that "coral reefs in locations with more
frequent warm events may be more resilient to future warming," which
suggests that taking a little extra heat every once in a while prepares
corals to better deal with less frequent but more extreme heat waves when they inevitably do occur.